Many of those gains were very small. The economy was in horrible shape at the end of the banking/housing crisis which began in 2008, so it really had nowhere to go but up.
I don't see what Obamacare has to do with this, though. Regardless of when it was signed into law, the main portions of it didn't take effect until 1/1/14, and it's had all kinds of failures and increased costs sharply for those buying their own health insurance (who aren't getting subsidies).
If you are middle class and paying for your own health insurance, Obamacare has been a disaster for you.
You know what a cheap Jew I am, and despite my best efforts to price shop, I'm paying more than double today for essentially the same health care plan I had just 2.5 years ago.